Composites or multi-layers of polymer films are employed in packaging various items such as, for example, yogurt, condiments, beverages, preservatives and the like. Saran polymers are employed in composites to provide the composite with oxygen and water barrier properties to prevent spoilage. Another layer(s) sometimes employed in such composites are polyamides which provide the composite with toughness, temperature resistance, abrasion resistance, and aroma barrier properties. Such composites can also contain, in addition to the polyamide, other .alpha.-olefin polymers such as high density polyethylene or linear low density polyethylene and the like which provide the compoiste with a heat seal layer due to low temperature resistance and ease of melting. One problem which must be solved in the formation of such composites is the total absence of adhesion between the Saran polymers and the polyamides. It is also well-known that polyolefins such as linear low density polyethylene have no adhesion to polaymides either. It is therefore, desired to develop a method which would permit the adhesion of the Saran polymers for oxygen and water barrier properties to polyamides for the temperature resistance and aroma barrier, and to permit such a composite to be sealable by heating or subjecting the composite to radio frequency energy.
Currently, one method for forming such composites is to apply a coating of a Saran latex to the polyamide but the coating applied is minimal and no polyethylene is employed. Another method is to employ a tie or glue layer such as an ethylene/vinyl acetate polymer which is either co-extruded, laminated, or extrusion coated onto the polyamide. The Saran polymer is then applied to the side with the ethylene/vinyl acetate polymer by lamination, extrusion lamination or as a latex with subsequent solvent removal.
It would be desirable to have a method for adhering polyamides to Saran polymers without having to employ an adhesive layer.